People in today's society have many different modes of transportation available to them, and many factors that determine when, where, and how each individual will travel from one place to another. In many cases, a person's movements have a set of defined, rational criteria, but those criteria can vary from person to person and from situation to situation.
When human movements can be predicted accurately, transportation systems may be studied to answer many interesting questions. For example, how might a transportation network be affected by a temporary or permanent change in design, where would be a good location for a new store, or how would policy decisions for a workforce affect transportation network loading?